The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
It is generally known that liquids can be delivered and gases can also be compressed by means of rotor pumps. An externally geared inner ring meshes with an internally geared outer ring for this purpose, wherein the inner ring is positioned eccentrically with respect to the outer ring and is driven by a suitable drive unit. If the inner ring has five gears, for example, then these mesh between six gear teeth of the outer ring. The fluid is drawn into five operating chambers and then displaced out of these with each revolution of the inner ring.
An internal gear pump of this kind is known from German Patent DE 299 13 367 U1, in which the outer ring is driven using a hollow shaft motor. A rotor bearing a permanent magnet is arranged around the outer ring, wherein the outer ring and the rotor are connected to each other in a suitable manner, so that the rotor can drive the outer ring. It is considered disadvantageous that an internal ring pump of this kind has large dimensions in the radial direction and that a large number of parts are required and must be installed.